Aromatic dicarboxylic acids, such as terephthalic acid and isophthalic acid, are used to produce a variety of polyester products. Important examples of which are poly(ethylene terephthalate) and its copolymers. These aromatic dicarboxylic acids are synthesized by the catalytic oxidation of the corresponding dialkyl aromatic compounds which are obtained from fossil fuels, which is disclosed in U.S. Patent Application 2006/0205977 A1), which is herein incorporated by reference to the extent it does not contradict the statements herein.
There is a growing interest in the use of renewable resources as feed stocks for the chemical industry mainly due to the progressive reduction of fossil reserves and their related environmental impacts. Furan-2,5-dicarboxylic acid (FDCA) is a versatile intermediate considered as a promising closest biobased alternative to terephthalic acid and isophthalic acid. Like aromatic diacids, FDCA can be condensed with diols such as ethylene glycol to make polyester resins similar to polyethylene terephthalate (PET) (Gandini, A.; Silvestre, A. J; Neto, C. P.; Sousa, A. F.; Gomes, M. J. Poly. Sci. A 2009, 47, 295.). FDCA has been prepared by oxidation of 5-(hydroxymethyl)furfural (5-HMF) under air using homogenous catalysts as disclosed in US2003/0055271 A1 and in Partenheimer, W.; Grushin, V. V. Adv. Synth. Catal. 2001, 343, 102-111. However, achieving high yields has proved difficult. A maximum of 44.8% yield using Co/Mn/Br catalysts system and a maximum of 60.9% yield was reported using Co/Mn/Br/Zr catalysts combination.
The crude FDCA obtained by the oxidation processes must to be purified before they are suitable for end-use applications. JP patent application, JP209-242312A, disclosed crude FDCA purification process using sodium hydroxide/sodium hypochlorite and/or hydrogen peroxide followed by acid treatment of the disodium salt to obtain pure FDCA. This multi-step purification process generates wasteful by-products.
Therefore, there is a need in the chemical industry for an inexpensive and high yield process for the purification of crude FDCA that does not produce waste products and lends itself to easy separation step(s).